The New Year has just begun and already you're finding it hard to keep those resolutions to junk the junk food, get off the couch or kick smoking.
There's a biological reason a lot of our bad habits are so hard to break - they get wired into our brains.
That's not an excuse to give up. Understanding how unhealthy behaviours become ingrained has scientists learning some tricks that may help good habits replace the bad.
"Why are bad habits stronger? You're fighting against the power of an immediate reward," said Dr Nora Volkow, director of the National Institute on Drug Abuse and an authority on the brain's pleasure pathway.
It's the fudge vs broccoli choice: Chocolate's yum factor tends to beat out the knowledge that sticking with veggies brings an eventual reward of lost kilos.
"We all as creatures are hard-wired that way, to give greater value to an immediate reward as opposed to something that's delayed," Volkow said.
Just how that bit of happiness turns into a habit involves a pleasure-sensing chemical named dopamine. It conditions the brain to want that reward again and again - reinforcing the connection each time - especially when it gets the right cue from your environment.
People tend to overestimate their ability to resist temptations around them, thus undermining attempts to shed bad habits, said experimental psychologist Loran Nordgren, an assistant professor at Northwestern University's Kellogg School of Management.
"People have this self-control hubris, this belief they can handle more than they can," said Nordgren, who studies the tug-of-war between willpower and temptation.
In one experiment, he measured whether heavy smokers could watch a film that romanticises the habit - called Coffee and Cigarettes - without taking a puff.
Upping the ante, they'd be paid according to their level of temptation: Could they hold an unlit cigarette while watching? Keep the pack on the table? Or did they need to leave the pack in another room?
Smokers who'd predicted they could resist a lot of temptation tended to hold the unlit cigarette - and were more likely to light up than those who knew better than to hang onto the pack, said Nordgren. He now is beginning to study how recovering drug addicts deal with real-world temptations.